So much for the theory that this was going to be a night for Tottenham Hotspur to measure themselves against one of the top teams in European football. Mauricio Pochettino may as well have waved a white flag from the moment he handed in the team-sheet as Borussia Dortmund tormented the Premier League club to such an extent that the second leg at White Hart Lane has already been rendered irrelevant.

Evasive about where his priorities lay on the eve of the game, Pochettino made it clear that it is the Premier League title or nothing for Spurs this season by making seven changes – only the suspended Dele Alli was enforced – from the side that drew against Arsenal on Saturday. By the time Harry Kane was brought on with 14 minutes remaining, Dortmund were rampant and the evening had turned into an exercise in damage limitation for Tottenham.

Dortmund were exhilarating to watch and it is easy to see why there is so much excitement in these parts about the way Thomas Tuchel has re-energised the club since replacing Jürgen Klopp as manager in the summer. Pierre-Emerick Aubameyang was outstanding up front and took his tally for the season to 33 goals in 38 appearances, the wonderfully gifted Henrikh Mkhitaryan ran the game from midfield and Marco Reus scored twice.

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Reus’s second was a moment of beauty and highlighted the chasm in class.

Dortmund swept from one end of the pitch to the other, completing 21 passes before the ball arrived at the feet of the Germany international, who then showed superb technique to clip a half-volley beyond Hugo Lloris.

With Dortmund in an identical position to Spurs in their domestic title race – both clubs are second and five points behind the leaders – it was hard to avoid the conclusion that Tuchel views the Europa League much more seriously than Pochettino. Dortmund’s manager made only two changes to his side and was rewarded with what he described as a “huge performance”.

As for Pochettino, the focus now turns to Aston Villa on Sunday and a game that Spurs simply have to win, not just to keep alive their title hopes but also to vindicate the way their manager approached this fixture.

“I’m very disappointed with the result,” Pochettino said. “It was a bad day at the office, we need to accept that. I have no regret because I think when we analyse we picked 11 to try to win the game. I think we started the first five minutes OK but then it was a very bad day for us.”

This could still turn into a historic season for Spurs but they quickly need to get back on track. Tottenham have picked up only two victories from their last seven matches and it was hard to see how Pochettino could talk about any positives on a night when his callow team were so comprehensively outplayed.

“We know the circumstances,” the Spurs manager said. “You need to accept some period in the season where sometimes it’s good and bad. The last few results have not been what we hope but I’m not worried. The players are very sad but that’s normal. We now have a big challenge on Sunday against Aston Villa, and we are in a very good position in the league to try and give our best.”

Dortmund were so impressive and the only surprise was that the game was half an hour old before they took the lead. Tom Carroll and Ryan Mason were overrun in central midfield, Nacer Chadli was anonymous up front and it was easy to feel sympathy for 18-year-old Joshua Onomah, who was starting only his fourth game for Spurs.

The early chance that Christian Eriksen swept into the arms of Roman Weidenfeller, with only 38 seconds on the clock, was no sign of things to come as Tuchel’s side began to go through their gears, targeting the space that opened up on the flanks, where Ben Davies, the Spurs left-back, and Kieran Trippier, the right-back, were horribly exposed at times.

Aubameyang had already seen a goal disallowed for offside and volleyed on to the roof of the net when he put Dortmund ahead. Marcel Schmelzer picked up possession wide on the Dortmund left and his measured cross was met by the Gabonese, who climbed above Davies to send a powerful downward header into the corner.

If the interval provided Spurs with some respite, there was no let-up after the restart. Mkhitaryan, with yet another sublime pass, set Aubameyang free inside the Spurs area and the striker’s low shot slid across goal to Gonzalo Castro, who struck the outside of the post.

Dortmund, however, did not have to wait long for their second. A short-corner routine saw Castro whip in a cross that Neven Subotic, who had been on the pitch for only three minutes, flicked on for Reus, ghosting in at the far post, to volley powerfully into the roof of the net.

The best, however, was still to come, with Reus applying the coup de grace with his delightful finish after Castro had picked him out with a pitching wedge of a pass. Dortmund were enjoying themselves by that point and came close to adding a fourth in the closing stages.

Pochettino later talked about how Spurs would “still try and fight for the tie” but he was kidding nobody.